There is known a device for converting a reciprocating motion into unidirectional rotation (PCT/SU90/00280) in the form of a non-self-braking helical mechanism housed in a casing. The helical mechanism has a driving member in the form of a screw with a unit for applying an axial force, and a driven member in the form of a nut journaled in bearings inside the casing and connected to the driving member through rolling bodies. The driven and driving members make up a helical rolling transmission. Connected to the unit for applying an axial force is a mechanism for generating and varying this force fashioned either as a controllable power cylinder, or as a hinged-lever system capable of smoothly varying the ratio between the lever arms.
However, the known hinged-lever mechanisms for generating and varying an axial force produce radial component forces that negatively affect the efficiency of the axial force application unit in operation by causing its deformation and skewing. Also, the power elements of such systems, for example, the casing taking up the forces of reaction from forces exerted on the driven member must have substantial dimensions and weight to provide the required rigidity.